In recent years, wireless communication environments have faced the problem of rapid increases in data traffic. In this regard, in 3GPP, dispersion of traffic by installing a plurality of small cells in a macro cell and increasing a network density is defined. A technique of utilizing small cells in this way is referred to as “small cell enhancement.”
The concept of a small cell can include different types of cells that are smaller than macro cells (for example, femtocells, nanocells, picocells, microcells, and the like) that are arranged separately or to overlap macro cells. In one example, a small cell is operated by a dedicated base station. In another example, a small cell is operated such that a terminal serving as a master device temporarily operates as a small cell base station. A so-called relay node can be regarded as a form of a small cell base station.
In order to cope with the rapid increases in data traffic, concentrating cells may be considered, but in this case, inter-cell interference may increase. When small cells are introduced, interference may occur between a small cell and a macro cell in addition to between small cells and between macro cells. Under such a communication environment, communication throughput in a user terminal (hereinafter, also referred to as “user throughput”) can be reduced by interference, and thus a technique of preventing a decrease in user throughput is necessary. As an example of such a technique, a technique of utilizing a plurality of frequency bands in one wireless communication system or performing dynamic frequency control may be effective.
For example, in Patent Literature 1, a technique of performing a unidirectional handover of switching uplink (UL) communication from at least one UL component carrier on a first evolutional Node B (eNB) to a new UL component carrier on a second eNB is disclosed.
In Non-Patent Literature 1, an algorithm for allocating component carriers to a picocell or a remote radio head (RRH) including a plurality of RF units in LTE-A HetNet deployment is disclosed.